We want to have a nice experience when scrolling the terminal buffer using both alacritty and tmux on Debian linux.

When we run alacritty and tmux together and there's a lot of text on the screen (say, by invoking tree), we need to hit the following tmux key sequence to scroll back through the terminal history:

Ctrl+B 
[
PageUp

This is difficult. Others have asked about this.

We followed the workaround advice given by the author. We enabled mouse mode, and disabled faux scrolling in .tmux.conf:

set -g mouse on
set -ga terminal-overrides ',*256color*:smcup@:rmcup@'

In .alacritty.conf, the default scrolling key combination, Shift+PageUp, isn't too bad. We can just leave it commented to use it, but if we want to try our own settings, we can:

key_bindings:
#
# ...snip...
#
- { key: PageUp,   mods: Shift, action: ScrollPageUp,   mode: ~Alt       }
- { key: PageDown, mods: Shift, action: ScrollPageDown, mode: ~Alt       }
- { key: Home,     mods: Shift, action: ScrollToTop,    mode: ~Alt       }
- { key: End,      mods: Shift, action: ScrollToBottom, mode: ~Alt       }

Resolution

With the changes to .tmux.conf, we can now start an alacritty terminal, enter tmux, and scroll to our hearts' content, without using a difficult key combination.

🔥 It's FAST! 🔥

We found that scrolling through history with some basic command line apps wasn't negatively impacted.

When we entered tmux + alacritty, and then dumped a lot of text into less, or navigated man bash, we scrolled happily and without interruption.

These instructions probably apply to other terminal emulators, as well.

This is a happy time. 😄